Thermostatic device



June 10; 1930. v DORFMAN 1,763,137

THERMOSTATIG DEVICE Filed N ov. 1 0, 1927 2 Sheets-Sheet 1 .Iuhe 10, 1930. H; D QR MAN 1,763,137

- THERMOSTATIC DEVICE Filed Nov. 10, 1927 2 Shee tsSheet 2 INVENTOR ATTORNEY Patented June 10, 1930 um'ran STA ES PATENT oat-ice mm I). new, WELD, OHIO, ASSIGNOB TO WESTINGHOUSE mo h 'IANUIAO'IUBII'G CODANY, CORPORATION 01 PENNSYLVANIA eflicient in its operation and factured and installed.

. 'rrmnuos'ranc' 1m Application am Iovember 10, 1921. Serial lo. mi.

The invention relates to thermostatic devices and particularly to thermostatic switches.

An object of the invention is to provide a thermostatic switch that shall be simple and easily manu- And a fprther object of-the invention is to provide a thermostatic switch for electric energy translating devices that shall be operable to protect the device from moderate overloadslong continued and from abnormal or severe overloads of short duration.

In practicing my invention, I provide a thermostatic switch, for protecting electric motors and similar devices from overloads,

with a heater for heating the thermal element of the switch by conduction and a heater for heating the thermal element by-radiant heat,

both heaters being energized by current traversing themotor. The conduction heater efiect's actuation oi the switch, and consequent deenergization of the motor, respon sive to moderate overloads long continued, and the radiant heater becomes eflective and responsive to abnormal overloads of short duration to actuate the switch.

For a fuller understandin of the invention reference may be had to t e following description taken in-conjunction with the accompaying drawings, in which:

Figure 1 is a bottom plan view of a ther-' mostatic switch base for the device, embodyi the invention; Tig. 2 is a top plan view of the same base;

Fig. 3 is a. view partially in side elevation and artiall in section, of a thermostatic switc em ying the invention; and

Fi 4 and 5 are schematic illustrations of circuits and apparatus embodying the invention.

In the drawin a base 1. is illustrated on a bottom face of w ch are disposed concentric washers 2 and 3, of suitable insulating material, haying difierent diameters. The washers are provided with openings at the center thereofwhich are in alinement with an opening at substantially the central portion .of

the base 1. The washers maybe securedto the ba by an internally screw-threaded eyeofthe contact members 5120 let or bushing 4, one edge of which may be peened over againstthe'base andth'e other of which may be eened over a ainst the surface of washer 3 1n order to ho d .thewashers securely thereagainst. i I

A plurality of contact members 5 .9, inclusive, of arcuate sha e are disposed along the circumference of t e washer 3 and rest upon the face of the washer 2. i The upper face of the base 1 is provided with a heating element 10 that is disposed between sheets 11 and 12 of electric-insulating material. In order that the contact members 5.,t o 9, inclusive, the heating element 10, and the sheets 11 and 12 may be secured firmly to the base 1, a rivet 13 and terminal mem-' bers 14 'to'17, inclusive, are provided.

As shown in Figs. 1 and 2, the rivet 13 extends through the sheets 11 and 12, the base 1 and the contact member 5, the lower end of the rivet being peened over against the contact member 5 in order to hold it rigidly in q place.

lower ends of the terminals-being peened over against the facespf the contact mem-" bers thereby holding them securely in place. The ends of the resistor element 10 may be secured to the terminals 14 and 15,in order.

- to make electrical contact therewith.

As shown in Fig. 1 of the drawin a heating element or resistor 18 of the ra 'ant heat type is secured against the outer surface of the washer 3 by a' lug 19., The ends of the resistor may be secured to the ends of the terminals 14 and 15, respectively, either by welding or other suitable methods.

In order that an electric circuit may be controlled between the terminals 16 and 17, a

bimetallic disc 21 having contact buttons.22 to 24, inclusive, secured theretois provided. The contact buttons may be insulated from the disc by insulating washers 25, only one of which is' shown (see Fig. 3). The contact buttons are so positioned that adjacent ends be bridged thereby.-

9, inclusive, may 1 The disc 21 may be secured to the base by means of a stud bolt 26 that has screw-thread engagement with the bushing 4. The initial pressure existing between the contact buttons 22 to 24, inclusive, and the contact members 5 to 9, inclusive, may be adjusted by the stud bolt 26 by so turning it that the disc 21 is brought either closer to or moved farther away from the base 1.

The disc 21 may be of the type disclosed in the patent to J. A. Spencer, No. 1,448,240. This disc has the characteristic that when normally cool, or when the temperature is below a predetermined value, the shape thereof may be substantially that shown in Fig. 3 of the drawings, but when heated to a higher temperature of a predetermined value, the disc will assume a reverse curve position with a snap motion thereby effecting disengagement of the contact buttons 22 and 24, inclusive, from their cooperating contact members 5 to 9, inclusive.

It is evident from Figs. 1, drawings that the resistor elements 10 and 18 are connected in parallel circuit with each other, but in series between the terminals 16 and 17 of the switch. Therefore, any current which flows between the terminals 16 and 17 will flow through the resistor elements 10 and 18.

The resistor elements may be so proportioned that, if a predetermined value of current say, for example, 10 am eres, flows through the resistance elements or a period of twenty minutes, the resistance-element 10 will have generated sufiicient heat to cause the bimetallic disc 21 to have been heated to its operating temperature by conducted heat from the base 1. The resistance element 18 may be so proportioned that, if ten amperes flows therethrough, sufficient heat will not have been enerated thereby to affect the operation 0? the disc 21. However, this element may be so proportioned that, if a current of say, for example, thirty amperes flows therethrough for a period of two minutes or less, the element will have generated sufficient radiant thermal energy to heat the disc '21 to its operating temperature.

An application of the thermostatic switch illustrated in the drawings in which the heating elements 10 and 18 are connected in parallel circuit relation with each other to an electric motor 28 is illustrated in Fig. 4

- of the drawings. In this application, with a given design of resistor elements 10 and 18, the element 10 will be responsive to moderate current overloads to cause the motor 28 to be deenergized when the moderate overload has persisted for a relatively long period of time. If, however, the motor 28 has been subjected to a severe overload so that a current of substantially short circuit value flows therethrough, the resistor 18 will respond almost instantly to generate sufficient radiant 2 and 4 of the thermal energy to effect operation of the thermostatic switch and a consequent deenergization of the motor.

When the resistor elements 10 and 18 are connected in parallel as shown in Fig. 4, the switch may be utilized for protecting a motor having a full-load current.rating of say 30 amperes, but if the switch were to be utilized with a motor having a full-load current rating of 15 amperes the resistance elements would not generate suflicient thermal energy to actuate the switch to its open circuit position in time to protect the motor from overheating. In order that the switch may be applicable to themotor of the smaller rating without changing the resistance of the elements 10 and 18, the resistance elements may be connected in series as shown in Fig. 5 of the drawings. Stated in another way, if the elements 10 and 18 are connected in parallel, the switch may be applied to a motor of a given horse power and designed for use on a 110-volt circuit, but if a motor of the same horse power but designed to operate on 220 volts, the resistance elements may be connected in series.

In Fig. 5 of the drawings, one terminal of the resistance element 10 is connected to one terminal of the motor and the other terminal thereof is connected to a terminal 17 of the switcln Since the resistor element 18 remains connected to the terminals 14 and 15, it is evident that the resistor elements 10 and 18 are connected in series circuit relation to each other and the motor 28.

It is to be noted that the moment the switch has been actuated to its circuit opening pos1- tion, the resistor elements 10 and 18 are deenergized whether they be connected in series or parallel, thereby permitting the disc 21 .to cool and to cause it to return to its circuit closing position automatically. However, if the motor 28 is still subjected to a severe overload, the switch will be actuated to its open circuit position promptly, in order to insure protection of the motor from excessive temperatures which may result from excessive current flowing therethrough';

Various modifications may be made in the device embodying the'invention without departing from the spirit and scope thereof. It is desired, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. In a thermal relay for an electric motor, in combination, a thermostatic switch for the motor, meansresponsive to a relatively small" value of current long continued for heating the switch to its operating temperature by conducted heat, and a second means re- 1 sponsive to a relatively large value of current of short duration for heating the switch to its operating temperature by radiant heat.

2. In a thermal relay, in combination, a

base, a plurality of contact members secured thereto, a bimetallic disc su ported b said base, contact members carrie thereby or cooperating with said plurality of contact members a heating unit on said base for causing the disc to be actuated res onsi've to heat conducted thereto from the ase, and a heatin' element supported b said base and dispose between the disc an base for causing actuation of the disc responsive toradiant heat.

3. In a thermal relay, in combination, a

base, a plurality of contact members secured thereto, a bimetallic discsu ported b said base, contact members carrie thereby or cooperating with said lurality of contact mem- Eersed by current traversing the translating evice.

In testimony whereof, I have hereunto subscribed my name this 2d day of November,

HILLER D. DORFMAN.

bers, means on said ase for heating said base a to cause actuation of the disc responsive to heat conducted thereto from the base, and means supported by said base for heating said disc y radiant heat to cause actuation thereof.

4. In a thermostatic circuitcontrollin de vice for protectin electric motors both rom moderate overloa bination, a thermostatic switch for controlling the motor, means responsive to moderate overloads for causing the switch to be actu ated, and a second means responsive to abnormal overloads for causing the switch to be actuated. v v

5. In a thermostatic circuit controlling device for protectin electric motors both from moderate overloa s long continued and abnormal overloads of short duration, in com bination, a thermostatic switch. for controllong continued and abnormal overloads of short duration, in comling the -motor, a heating element responsive to moderate overload motor current for causing the switch to be actuated by conducted heat, and a heating element responsive to abnormal overload motor current for,causingthe switch to be actuated by radiant heat.

prisin 6. A base for a thermostatic switclli com;

a supportin plate a plura ity 0 space contact memiers disposed on said plate and insulated therefrom, a conduction heating unit disposed on one side of the plate,

and a radiant heating unit disposed on the other side thereof. y

7. In a thermostatic circuit controlling device for electric energy translating devices, in

combination, a base, stationary contacts supported thereby,.a thermostatic element, contacts carried thereby for cooperating withdiant heat,said heating elements traieo 

